Combination of lathe and thread-cutting attachment



Sept. 1, 1970 J. BlRGMAYER ET AL' COMBINATION OF LATHE AND THREAD-CUTTING ATTACHMENT Filed June l2, 1968 mi. IWL..

United States Patent O 3,526,161 COMBINATION F LATHE AND THREAD- CUTTING ATTACHMENT Josef Birgmayer and Karl Husarik, Linz, Austria, as-

signors to Vereinigte Osterreichische Eisenund Stahlwerke Aktiengesellschaft, Linz, Austria Filed `lune 12, 1968, Ser. No. 736,483 Claims priority, application Austria, Sept. 22, 1967, A 8,620/67 Int. Cl. B23b l/ 00 US. C1. 82-5 9 Claims ABSTRACT OF THE DISCLOSURE A carriage is mounted on a lathe bed and movable in a longitudinal direction relative to said bed. A cross slide is mounted on said carriage and movable relative to said carriage transversely to said longitudinal direction. Carriage drive means are mounted on said bed and operable to move said carriage relative to said bed in said longitudinal direction. An attachment base is mounted on said cross slide. An attachment slide is slidably mounted on said attachment base for advancing and withdrawing movements, which are transverse to said longitudinal direction. A tool is carried by said attachment slide. A huid-operable piston motor is carried by said attachment base and operable to impart an advancing movement to said attachment slide. A stop roll is rotatably mounted on said attachment base and formed with a plurality of angularly spaced radial bores. A plurality of stop screws screws are axially adjustably mounted in respective ones of said bores. A ratchet is coupled to said roll. An actuating pawl is coupled to said attachment slide and adapted to impart an incremental angular movement to said ratchet in response to a withdrawing movement of said attachment slide. Said roll is rotatable by said pawl and ratchet to successive angular positions, in which successive ones of said stop screws are in the path of the advancing attachment slide and limit the advancing movement thereof. A plunger is carried by said attachment base and extends and is movable relative thereto in said longitudinal direction and arranged normally to move in unison with said attachment base. A rod is carried by said `bed and extends in said longitudinal direction. Two stops' are carried by said rod and adjustable along the same. Said stops extend into the path of said plunger and are arranged to move said plunger relative to said attachment base when said carriage is moving in said longitudinal direction while said plunger is in engagement with one of said stops on said rod. Means comprising an admission control switch are provided for controlling the admission of lluid to said piston motor. Said admission control switch is arranged to be actuated in response to said movement of said plunger relative to said attachment base. A carriage drive'control switch is actuable by said attachment slide and arranged to initiate a forward movement of said carriage in response to an advancing movement of said attachment slide and a rearward movement of said carriage in response to a withdrawing movement of said attachment slide.

This invention relates to an automatic thread-cutting attachment to be mounted on the carriage of a lathe.

A known attachment of this kind is driven by a universal joint shaft connected at its input end to the tailstock end of the lead screw of a center lathe. In that known attachment, all movements which are required are controlled and performed by a ratchet wheel cooperating with camwheels. In this connection it is a disadvantage that diterent camwheeels of an appropriate size and shape 3,526,161 Patented Sept. 1, 1970 ice must be used for cutting threads having different lengths and that the maximum length of the threads which can be cut is restricted because camwheels exceeding a certain size cannot be accommodated. Besides, the depth of cut is always the same in all successive cutting operations so that it is not possible to select a large depth for the iirst cut and progressively decreasing depths for the successive cuts although this would be desirable for a reduction of the machining time and for an improvement of the surface nish of the side faces of the threads. 'Ihe known attachment has also the disadvantage that the tool cam be withdrawn when the thread-cutting operation has been; completed but does not automatically return to the initial position for the rst cut and that the attachment must be deenergized by hand. Besides, the entire attachment is mounted on the carriage of the lathe in such a manner that the attachment would obstruct other operations to be performed on the lathe so that the attachment must be removed before the lathe is available for other turning operations.

VIt is an object of the invention to eliminate these disadvantages and provide an automatic thread-cutting attachment in which the number of cuts desired in cutting a screw thread and the depth of each cut can be selected as desired, the length and lead of the thread are not limited except by limits imposed by the lathe itself, the attachment automatically returns to the initial position for the first cut of the next thread and is then automatically stopped when a thread has been completed, and the attachment does not obstruct other turning operations when out of use.

This object is essentially accordingly accomplished to the invention in that an attachment base is adapted to be secured to the cross slide mounted on a carriage, which during thread cutting is moved in the usual manner by the' lead screw, said attachment base carries an attachmentv slide, which carries the tool and is adapted to be advanced toward the workpiece transversely to the axis thereof by a hydraulic or pneumatic piston motor and to be withdrawn to its initial position preferably by spring force,

1 the attachment base also carries a stop roll or the like member, which is provided with a plurality of angularly spaced radial bores for receiving adjustable stop screws, said roll is incrementally rotatable with the aid of a ratchet and an actuating pawl, which s actuated by the attachment slide as the latter returns, said stop screws are successively moved by said rotation to operative positions'in which they limit the advance of the carriage, the bed or headstockof the lathe carries a rod orvthe like member, which is parallel to the spindle and carries two stops, which are adjustable to the desired length of the thread, a plunger is associated with said stops and extends parallel to the rod or the like member and is adapted to be displaced when striking either ofthe two stops so as to actuate a switch for controlling the admission of pressure to the piston motor, and another switch is provided which acts on the means for driving the carriage and is movable by the carriage and arranged to initiate a forward movement of the carriage in response to an advance of the attachment slide and rearward movement of the carriageA in response to a withdrawal of the attachment slide. Just as in a usual thread-cutting operation performed without an attachment, a movement parallel to the axis of the workpiece is imparted to the tool by the lead screw, which moves the carriage. This has the advantage that threads of any length and lead which canbe cut on the lathe alone can also be cut with the aid of the attachment. The attachment slide causes the tool to perform the advancing and withdrawingmovement otherwise imparted to the tool by the cross slide. The advancing movement of the* attachment slide is limited by the stop screws of the stop roll. As the stop screws are adjustable in the radial bores, the advancing movement of the attachment slide and with it the advanced position of the tool and the depth of cut can be varied. During each withdrawing movement of the attachment slide, the stop roll is rotated by means of the actuating pawl and the ratchet to move the next stop screw into operative position. Dilerent depths can thus be selected for individual cuts. The number of stop screws which are used in cutting one thread will depend on the number of cuts desired for the screw thread. An automatic sequence of operations is enabled by the two switches. When the plunger strikes at the end of a cut the stop at the headstoek end of the rod which is parallel to the lead screw, the switch actuated by the plunger interrupts or reverses the admission of pressure to the piston motor to initiate the withdrawing movement of the attachment base and tool. During the withdrawing movement of the attachment base, the latter acuates the second switch, which initiates a rearward movement of the means for driving the carriage so that the tool returns to its initial position. As soon as the plunger strikes the second stop during the rearward movement of the carriage, the irst switch is actuated to reverse the piston motor so as to advance the attachment slide, the latter then changes over the second switch to initiate a forward movement of the carriage, and the next cut begins. The length of the advancing movement of the attachment slide has now been changed because the stop roll was rotated during the withdrawing movement of the attachment slide and the advancing movement of the attachment slide is now limited by another stop screw. It will be understood that the length of the thread can be adjusted by means of the stops which are adjustably mounted on the rod which is parallel to the lead screw. The entire attachment is relatively simple in structure and has the great advantage that special camwheels of other replaceable parts are not required for a cutting of threads differing in length and lead and for dilerent depths of cut.

To ensure a withdrawal of the tool to the initial position for the irst cut when a thread has been completed and a subsequent automatic deenergization of the entire attachment, a development of the invention resides in that the stop roll or the like member is biased by a return spring and is adapted to be held in its various angular positions against the tension of the return spring by balls or the like detent elements, which are resiliently urged into detent openings corresponding to said angular positions, the detent spring acting on the ball or the like detent element bears on a slider, which is adapted to be locked in either of two positions, said slider is articulatedly connected to the actuating pawl so as to provide for a freedom of movement of the latter and in response to the withdrawal of the attachment slide after the last is automatically movable with the aid of a trip pin, which is insertable into the stop roll or the like and causes the slider to assume a position in which the detent spring no longer holds the ball or the like detent member in the respective detent opening and the actuating pawl is disengaged from the ratchet wheel, a switch is provided, which is actuable by the slider during the movement of the latter and upon the release of the stop roll deenergizes the means for driving the attachment and the carriage as soon as the same has been returned. When the slider is moved the second position from the position in which the *ball is urged into the detent opening and in which the actuating pawl engages the ratchet wheel, the stop roll will no longer be held against rotation and will be reversely rotated by the return spring to the initial position, in which the first stop stop screw is in operative position. At the same time, the slider actuates a switch which is included in the circuit in such a manner that the entire means for driving the attachment are deenergized as soon as the switchV which is actuated by the plunger is changed over at the end of the rearward movement of the carriage. When the attachment is reenergized, the attachment slide will engage the iirst stop screw so that the tool is in position for the irst 4l cut and the iirst cut of a new thread is initiated. All returning operations are initiated with the aid of the release pin and the latter may be inserted at a selected point of the stop roll or the like to determine the time when deenergization will be effected.

According to the invention, means for moving the slider to the position for releasing the stop roll or the like member comprise a pusher arm, which is parallel to the slider and in response to the withdrawing movement of the attachment slide is moved against the force of a spring by a run-up cam, and a lever, which is pivoted to the pusher arm and articulatedly engages the slider and bears on the trip pin from time to time so as to form a fulcrum, whereas the means for returning the slider comprises another lever, which is pivotally, movable, also by a run-up cam, in response to the advancing movement of the attachment slide. During each withdrawal of the attachment slide, the pusher arm is displaced against the spring force but the slider will generally not follow this displacement because the lever is only pivotally connected to the pusher arm at one end and to Ithe slider on the other end and for lack of a xed support cannot transmit force. As soon as the trip pin moves in front of the lever to form a fixed fulcrum in the last angular position of the stop roll, the lever will act like a double-armed lever and will displace the slideropposite to the displacement of the pusher arm.

A particularly suitable design will be obtained if the stop roll and the ratchet are coaxial and preferably integral and the detent openings extend axially and are disposed between the radial bores for the stop screws and the ratchet teeth and radial bores for selectively receiving the trip pin are provided on another peripheral circle.

The entire attachment is mounted according to the invention on the cross slide at that end thereof which is opposite to the crank handle for moving the cross slide. It will lthus be opposite to the normal station of the lathe operator and will not interfere with other turning operations. The stops on the rod which is parallel to the lead screw may be pivotally movable to a position in which they do not limit lthe carriage movement.

The invention is illustrated by way of example on the drawing, in which:

FIG. 1 is a diagrammatic top plan view showing an automatic thread-cutting attach-ment and FIG. 2 is a vertical sectional view taken on line II-II in FIG. 1.

The attachment base 1 is mounted on the cross slide (not shown) of a center lathe at that end of said cross slide which is remote from the crank handle for moving said cross slide. An attachment slide is movable transversely to the axis of the workpiece 4 and guided on the attachment base. The attachment slide 5 carries a tool holder 2, which is provided with a tool 3. The attachment slide is displaceable by a hydraulic piston motor, which consists of a cylinder 6 and a piston 7. The cylinder 6 is mounted on the attachment base 1. The piston 7 is biased by a compression spring 8 and has a piston rod 9, which is connected to the attachment slide 5. A double poppet valve 10 serves to control the piston motor. When the piston 7 admits the hydraulic or pneumatic pressure fluid, the attachment slide 5 is advanced toward the workpiece 4- against the force of the spring 8. When the cylinder 6 is connected to the exhaust, the spring 8 will impart a withdrawing movement to the attachment slide.

A stop roll 11 is `rotatably mounted on a vertical axis on the attachment base 1. The stop roll 11 has a multi- -plicity of angularly spaced radial bores 12 for receiving adjustable stop screws 13 and at its lower end carries ratchet teeth 14. Between the radial bores 12 and the ratchet Iteeth 14, detent openings 16 are provided on one peripheral circle and radial bores 17 for selectively receiving a headed trip pin 18 on a higher peripheral circle. A return spring 19 acts by a pulling cable on the stop roll 11 and tends to reversely rotate the latter to an initial position, which is defined by stops 20. A lever 21y` is connected to the base 1 by a pivot 22. An actuating pawl 23 is pivoted to the lever 21 and engages the ratchet teeth 14. A spring 24 urges the actuating pawl into the spaces Vbetween the ratchet teeth. Another spring 25 biases the lever 21. When the attachment slide 5 is being withdrawn, a run-up cam 26 swings the lever 21 in a counterclockwise sense so that the stop roll 11 is advanced one tooth in the clockwise sense. In each angular position, the stop is held against the tension of the return spring 19 because a spring 28 urges a ball 27 into the respective detent opening 16. The spring 28 'bears on a slider 29. A detent device 30 can lock the slider 29 in either of two positions. When the slider 29 is displaced to the second position to the right from the position shown in FIG. 1, the force of the spring 28 will no longer be suicient to urge the ball 27 into the respective detent openings 16. Besides, the actuating pawl 23 is lifted from the ratchet teeth 14 because a pin 31 carried by the pawl enters a window of the slider 29 so that the actuating pawl has sufcient freedom of movement when the slider is in its left-hand position whereas the slider in its right-hand position engages the pin to hold the pawl spaced from the ratchet teeth. In this case the stop roll 11 is reversely rotated by the return spring 19 into the initial position, which is defined by the stops 20.-

The slider 29 is displaced by a pusher arm 32, which ',is parallel to the slider andduring the withdrawing movement of the attachment slide`5 is displaced by a run-up cam 26a to the left, toward the stop roll, against the force of a spring 33. A lever 34 is pivoted to the pusher arm-32 and slidably pivoted to the slider 29. The lever 34 carries approximately at its center an upstanding pin 35. During a displacement of the pusher arm 32, the lever 34 is `swung -about its point of engagement on the slider 29, but the latter is not displaced thereby. When the stop-roll 11 has-'been rotated to such an extent that the trip pin 18 is adjacent to the pin 35, the latter will bear v on the head of the trip pin 18 to form a fulcrum for the lever. 34. During a displacement of the pusher arm 32 to the left, the slider 29 is now displaced to, its right-hand position, in whichthe stop roll is released for a reverse rotation to its initial position. The slider-29 is returned by a, pivoted lever 35, which is swung in the clockwise sense by a run-up cam 26b duringthe advance of the attachment slide.Also during the advance of the attachment slide, the lever 21 is swung under the action of the spring 25 so that the actuating pawl 23 engages the next ofthe ratchet teeth 14.

The mode of operation of the attachment according to the invention is as follows: It is assumed that the carriage and with it the attachment are in their initial position, in which the tool 3 is withdrawn from the workpiece 4 and is spaced in the direction of the workpiece laxis from the workpiece toward the tailstock. A start key is depressed to initiate the automatic thread-cutting sequence. The valve 10 now connects the pressure line to the cylinder 6, the piston 7 is displaced against the force of the spring 8 so that the attachment slide 5 is advanced until its stop part 44 engages the first stop screw 13 of lthe stop roll 11, which is also in its initial position. In response to the advance of the attachment slide 5, the -switch 42 initiates the forward movement of the carriage so that the rst cut is taken. At the end of this cut, the plunger strikes the stop 38 and is displaced to actuate the switch 41 so that the valve 10 is moved to the position in which the cylinder 6 is connected to exhaust. The

, spring 8 is now effective to withdraw the entire attachment slide 5. During this withdrawal of the slide, the run-up cam 26 swings the lever 21 and with it the actuating pawl 23 so that the stop roll 11 is advanced one tooth with the aid of the ratchet teeth y14, and the next stop sc'rew 13 assumes an operative position. The run-up cam 26C operates the switch 42 to initiate the rearward movement of the carriage. The pusher arm 32 is displaced by the run-up cam 26a but this displacement does not affect the slider 29.

The rearward movement of the carriage is limited in that the plunger 40 strikes the stop 39. The resulting displacement of the plunger causes a shifting of the switch 41 and of the valve 10. The latter now connects the cylinder 6 to the pressure line so that the attachment slide 5 is again advanced and the switch 42 initiates the forward movement of the carriage. During the advance of the attachment slide 5, its stop 44 strikes the second stop screw, which is now in operative position. The second screw is spaced by any desired angle from the first so that the tool is advanced further and a new c-ut having a selected thickness is taken. During the advance of the attachment slide, the pusher arm 32 and the lever 34 return to their initial position. Finally, the spring 25 urges the lever 21 to engage the actuating pawl 23 with the next ratchet tooth. These sequences are repeated until the desired last cut has been taken. When this cut has been completed, the plunger 40 strikes the stop 38 so that the switch 41 and valve 10 are shifted to initiate the withdrawing movement of the attachment slide, whereas. the switch y42 initiates the rearward movement of the A rod 37 extending parallel to the lead screw is mountedv onpthe bed or headstock of the lathe and carries two adjustable stops 38, 39. A plunger 415` for actuating a switch 41 is associated with these stops. When striking the stop 38, the plunger 40 shifts the switch 41 so that ther-valve 10 exhausts pressure uid from the cylinder 6 and the spring 8 can withdraw the attachment slide 5 from the workpiece. The engagement of the pusher 40 with the stop 39 will then result in a shifting of the switch and valve in the opposite direction so that the cylinder 6 is connected to the pressure conduit and the attachment slide 5 is advanced against the force of the spring 8 until the-attachment slide 5 engages that stop screw 13 which is in operative position. Another switch 42 is actuated by the attachment slide 5 through the intermediary of a run-up cam 26C and serves to initiate a rearward movement of the carriage in response to a withdrawing movecarriage. During the withdrawal movement of the attachment slide 5, the pusher arm 32 is displaced to the right. At this time, the head of the trip pin 18 constitutes a fixed bearing for the pin 35, as is shown in FIG. 2,

so that the lever 34 acts like a double-armed lever having a fulcrum at the end of the trip pin. The slider 29 is -now displaced to the right and is held in its new position |by the detent device 30. When the slider is in this position, the stop roll 11 is released and under the tension of the return spring 19 returns to its initial position. Whereas ment of the attachment slide and a forward movement of the actuating pawl 23 is moved too, it is disengaged from the ratchet teeth. During the displacement of the slider 29, the switch `43 was actuated to deenergize so that the rentire attachment is deenergized when the carriage has completed its rearward movement and the switch 41 is actuated. The attachment is now ready to cut a new thread, which is identical to the one cut before.

When the next cut is initiated by an advance of the attachment slide, the slider 29 is returned to its operative position by the run-up cam 26b and the lever 36.

To set up the attachment for a specific program, the valve 10 is shifted to admit pressure to the piston 7 so that that attachment slide is advanced until its stop 44 engages the first stop screw 13. The cross slide mounted on the carriage is now advanced until the tool 3 just contacts the periphery of the workpiece 4. When this position has been reached, a dial gage 45 is secured to the attachment slide in such a manner that it gives a Zero reading when contacting the attachment base 1. The carriage is now moved toward the tailstock until the tool is spaced to some extent from the workpiece. The cross slide is then further'advanced toward the workpiece by an amount which corresponds to the depth desired for the iirst cut or the first stop screw, which is in operative position, is adjusted by such amount. The plunger 40 is then manually reciprocated to rotate the stop roll as described hereinbefore to the next angular position, in which the second stop screw is in operative position. This stop screw is now adjusted with the aid of the dial gage 45 to the depth desired for the second cut. The procedure is repeated until stop screws in a number which corresponds to the desired number of cuts have been adjusted to the respective depths of such cuts. Finally, the trip pin 18 is inserted into the radial bore 17 which is associated with the last stop screw. Now the attachment is ready for operation.

What is claimed is:

1. The combination of a lathe, which comprises:

a bed,

a carriage mounted on said bed and movable relative to said bed in a longitudinal direction,

a cross slide mounted on said carriage and movable relative to said carriage transversely to said longitudinal direction, and

carriage drive means mounted on said bed and operable to move said carriage relative to said bed in said longitudinal direction,

and of an automatic thread-cutting attachment, which comprises:

an attachment base mounted on said cross slide,

an, attachment slide slidably mounted on said attachment base for advancing and with drawing movements, which are transverse to said longitudinal direction,

a tool carried by said attachment slide,

a Huid-operable piston motor carried by said attachment base and operable to impart an advancing movement to said attachment slide,

a stop roll rotatably mounted on said attachment base and formed with a plurality of angularly spaced radial bores,

a plurality of stop screws axially adjustably mounted in respective ones of said bores,

a ratchet coupled to said roll,

an actuating pawl coupled to said attachment slide and adapted to impart an incremental angular movement to said ratchet in response to a withdrawing movement of said attachment slide,

said roll being rotatable by said pawl and ratchet to successive angular positions, in which successive ones of said stop screws are in the path of the advancing attachment slide and limit the advancing movement thereof,

a plunger carried by said attachment base and eX- tending movable and relative thereto in said longitudinal direction and arranged normally to move in unison with said attachment base, a rod carried by said bed and extending in said longitudinal direction,

two stops carried by said rod and adjustable along the same, said stops extending into the path of said plunger and arranged to move said plunger relative to said attachment base when said carriage is moving in said longitudinal direction while said plunger is in engagement with one of said stops on said rod,

means comprising an admission control switch for controlling the admission of fluid to said piston motor,

said admission control switch being arranged to be actuated in response to said movement of said plunger relative to said attachment base, and

a carriage drive control switch which is actuable by said attachment slide and arranged to initiate a forward movement of said carriage in response to an initial advancing movement of said attachment slide and a rearward movement of said carriage in response to an initial withdrawing movement of said attachment slide.

2. The combination set forth in claim 1, which comprises spring means tending to impart a retracting movement to said attachment slide.

3. The combination set forth in claim 1, which comprises a lathe headstock carried by said bed and carrying said rod.

4. The combination set forth in claim 1, in which:

said pawl is actuable to impart an incremental angular movement to said ratchet in a iirst sense, and

said roll is formed with a plurality of detent openings spaced by the angle of said incremental movement, and which comprises:

a roll return spring connected to said roll and tending to rotate said roll in a second sense, which is opposite to said iirst sense, to an initial angular position, a detent element which is engageable with successive ones of said detent openings to lock said roll in respective ones of said angular positions, a slider which is movable between predetermined first and second positions and articulated to said actuating pawl, said slider being arranged to be normally in said first position and to provide freedom of movement for said actuating pawl when the slider is in said rst position, and to lock said pawl clear of said ratchet when said slide is in said second position, a detent spring arranged to be engaged by said slider and to urge said detent element against said roll when said slider is in said first position, and to be relieved by said slider when the latter is in said second position, slider-actuating means for moving said slider from ,said iirst position to said second position in response to a withdrawing movement of said attachment slide from a predetermined one of said stops of said roll, and a deenergizing switch for deenergizing said carriage drive means and said piston drive motor in response to the completion of the rearward movement of said carriage when said slider is in said second position. 5. The combination set forth in claim 4, in which said slider-actuating means comprise a trip pin,

said stop roll is provided with a plurality of angularly spaced pin-mounting means which are associated with respective ones of said radial bores and adapted to hold said trip pinto said roll, and

said trip pin is detachably held by one of said pinmounting means.

6. The combination set forth in claim 5, in which said stop roll and ratchet are coaxial,

said radial bores are spaced from said ratchet in the axial direction of said roll, said detent openings are arranged on a peripheral circle of said roll between said radial bores and ratchet, and

said pin-mounting means consist of additional radial bores arranged on another peripheral circle of said stop roll between said radial bores for said stop screws and said ratchet.

7. The combination set forth in claim 4, which comprises:

a trip pin carried by said step roll,

a pusher arm, which extends parallel to said slider,

a run-up cam arranged to displace said pusher arm in response to a withdrawing movement of said attachment slide,

a spring arranged to oppose said displacement of said pusher arm,

a lever which is pivoted to said pusher arm and said slider and adapted to be fulcrumed on said trip pin,

said pusher arm being arranged to move said slider from said rst position to said second position under the action of said run-up cam when said lever is fulcrumed on said trip pin,

another lever connected to said slider, and

another run-up cam arranged to move said other lever to return said slider from said second position to said iirst position in response to an advancing movement of said attachment slide.

8. The combination set forth in claim 4, in which:

said stop roll and ratchet are coaxial,

said radial bores are spaced from said ratchet in the axial direction of said roll, and

said detent openings are arranged on a peripheral circle of said roll between said radial bores and ratchet.

9. The combination set forth in claim 1, in which:

a crank handle is carried by said carriage adjacent to one end of said cross slide and operable to move said cross slide relative to said carriage transversely to said longitudinal direction, and

said attachment base is mounted on said cross slide at the other end thereof.

References Cited UNITED STATES PATENTS LEONIDAS VLACHOS, Primary Examiner 

